When I first played Anarchy Online I was really impressed by the maturity of the game. Even though it shows signs of age, the graphics still look good and the sheer amount of content, even in the free version, guarantees weeks and weeks of gameplay. The Science Fiction theme is also pretty nice and a welcome change from the drarvish/elvish Tolkienesque fantasy worlds a lot of MMORPGs are set in.
The developers have found a way to incorporate spellcasting of a sort into the game by allowing nano-technology to provide for mind-alteration, damage, healing 'spells', and a lot of boosts. There is a myriad of device you can buy that give different attributes a boost as well. Buying armour and laser guns is also pretty cool and the ability to have all kinds of crazy pets also adds to the fun.
I played the non-free version for a month and was amazed at the amount of new content it offered, but wasn't prepared to keep on paying the monthly fee (that plus I started to get addicted :|) I cancelled and opened a new free account immediately. It takes a little while to get acquinted with the game because of the huge amount of options, but luckily there are a lot of resources available. Soon, a new expansion for AO will be released, probably offering even more content, so it's bound to stay around for quite a while! Defintely worth playing!